Some image forming apparatuses are provided with a fixing device that fixes onto a recording medium a toner image carried on the recording medium by heating and applying pressure on the recording medium. The fixing device pushes a pusher member disposed on an inner peripheral side of a fixing belt toward a pressure roller disposed on an outer peripheral side of the fixing belt to form a fixing nip between the fixing belt and the pressure roller. Then, the fixing device heats the fixing belt via a heat source such as a halogen lamp disposed on an inner peripheral side of the fixing belt to heat a recording medium passing through the fixing nip.